In recent years, digital cameras that convert an object image into an electrical signal using an imaging device such as a charge coupled device (CCD) image sensor, a complementary metal-oxide semiconductor (CMOS) image sensor or the like, digitizes the electrical signal, and records the obtained digital signal have been widely used.
Single-lens reflex digital cameras include a phase difference detection section for detecting a phase difference between object images, and have the phase difference detection AF function of performing autofocusing (hereinafter also simply referred to as “AF”) by the phase difference detection section. Since the phase difference detection AF function allows detection of defocus direction and defocus amount, the moving time of a focus lens can be reduced, thereby realizing fast-focusing (see, for example, Patent Document 1). In known single-lens reflex digital cameras, provided is a movable mirror capable of moving in or out of an optical path from a lens tube to an imaging device in order to guide light from an object to a phase difference detection section.
In so-called compact digital cameras, the autofocus function by video AF using an imaging device (see, for example, Patent Document 2) is employed. Therefore, in compact digital cameras, a mirror for guiding light from an object to a phase difference detection section is not provided, thus achieving reduction in the size of compact digital cameras. In such compact digital cameras, autofocusing can be performed with light incident on the imaging device, i.e., with the imaging device being exposed to light. That is, it is possible to perform various types of processing using the imaging device, including, for example, obtaining an image signal from an object image formed on the imaging device to display the object image on an image display section provided on a back surface of the camera or to record the object image in a recording section, while performing autofocusing. In general, this autofocus function by video AF advantageously has higher accuracy than that of phase difference detection AF.